Photosolubilization image formation process with organic dmax. maintainers



United States Patent Olfice 3,493,373 Patented Feb. 3, 1970 U.S. C]. 9664 7 Claims ABSTRACT OF THE DISCLOSURE Process for forming a silver halide image by selectively exposing a photosoluble silver halide layer and dissolving the exposed photosoluble silver halide in a silver halide solvent characterized by having present during treatment in said solvent a .D maintaining amount of an auxiliary compound devoid of ionizable iodine, or oxidizing or reducing groups that are active at the working pH.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for forming images from photosoluble (photosolubilizable) silver halide layers. The present invention constitutes an improvement in a silver halide photosolubilization process by the use of an organic chemical compound adjuvant which helps to prevent dissolution of silver halide in unexposed areas while allowing dissolution to proceed in the exposed areas. Because of this characteristic, the adjuvant is referred to herein as a maximum density maintainer, or D maintainer.

Description of the prior art Photosolubilization image-forming processes and photosoluble layers and elements useful in the basic process are described in U.S. Patents 3,155,507 and 3,155,514-9, Nov. 3, 1964. Blake application U.S. Ser. No. 377,122, filed June 22, 1964 (refiled as Ser. No. 629,426, filed Apr. 10, 1967), and Haugh U.S. Ser. No. 478,421, filed Aug. 9, 1965. In these patents and applications there are described tests, and useful layers and processes for obtaining a positive silver halide image in a single processing step. Intensification of the image, e.g., by reduction to a black metallic silver image is an optional additional step.

SUMMARY OF THE INVENTION This invention pertains to an improvement in a photosolubilization process of forming a direct-positive silver halide image which process comprises:

(a) Exposing, imagewise, a photosoluble layer containing silver halide made relatively less soluble in a silver halide solvent by treatment with an organic compound containing sulfur and/or nitrogen and capable of forming a silver salt of lower solubility in water than silver chloride, and

(b) Dissolving the exposed silver halide in a silver halide solvent comprising an aqueous bath of an alkali metal or ammonium thiosulfate (preferably, alkali metal); the improvement being characterized by the presence, while said layer is in said bath at a pH of 3.5 to 11.0, of D maintaining amounts of the auxiliary organic compound devoid of ionizable iodine, or oxidizing or reducing groups that are active at the working pH, said compound having (1) at least one polar or ionic group, (2) at least one hydrocarbon group, and (3) a molecular weight between 61 and 300,

the organic compound being present in sufficient quantity to retard solution of the unexposed silver halide and within the range of 0.1 to 50 grams per liter of the aqueous bath. The auxiliary compound should be devoid of oxidizing groups because these tend to oxidize the silver salts of the compound of step (a) so that exposed and unexposed areas cannot be distinguished easily in terms of their rates of solution in a silver halide solvent.

The D maintaining organic compound effects an improvement by retarding the dissolution of silver halide preferentially in the unexposed as compared to the exposed areas of the photosoluble element. The presence of the D maintaining compounds has the advantage that more vigorous processing conditions may be used which can lead to greater speed. Also, greater latitude of processing conditions is permitted, e.g., in time, temperature and pH. Better control of contrast can be achieved in the presence of these compounds and, in the case of lthographic films, better halftone dot rendition is possible.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In practicing the process of the invention, a photosoluble silver halide layer as defined in Blake U.S. 3,155,507, preferably a layer of silver chloride emulsion insolubilized with 2-mercapto-4-phenylthiazole or a related mercaptan as disclosed in said patent is prepared. The element may advantageously have a photographic optical sensitizing dye associated with its silver halide crystals as disclosed in assignees copending application of Blake, U.S. Ser. No. 390,460 filed Aug. 18, 1964 (U.S.P. 3,384,- 485, May 21, 1968). The photosoluble layer is exposed, imagewise, to actinic radiation and then treated in an aque ous bath comprising from 0.1 to 2 moles per liter of a thiosulfate, e.g., sodium thiosulfate silver halide solvent and an organic DmflLx maintainer as defined above. An exemplary, practical, available 13 maintainer is 2-butoxyethanol in a concentration of 0.5 to 20 ml./1iter, preferably from 2 to 15 ml./ liter. The time and temperature of treatment in the aqueous bath are obviously dependent variables but at a temperature of F. the time should be about 30 sec. to 5 min. This treatment removes silver halide from the exposed areas at a much faster rate than from the unexposed areas, leaving a positive silver halide image. The presence of an organic compound such as Z-butoxyethanol further lowers the rate of dissolution of the unexposed silver halide, relative to that of the exposed silver halide, contributing to better image formation especially to higher densities in unexposed areas. A useful positive image can be produced, particularly for viewing by projection, by this single treatment, although a washing step is generally used. For most purposes, it is desirable to intensify the silver halide image, usually by treating with a photographic silver halide developer solution to reduce the image to one of black metallic silver. The silver halide image may be fogged prior to reduction by flashing to white light or, more conveniently, by use of a prefogged element such as described in assignees copending U.S. applications of Blade, U.S. Ser. No. 629,426 and Haugh U.S. Ser. No. 478,421 Other methods of intensifying the silver halide image, e.g., by toning, color developing, etc., are disclosed in U.S. 3,155,507.

Any of the various photosoluble silver halide elements described in the U.S. patents and Blake and Haugh applications listed above can be used in the process of this invention. These, of course, may be modified as described in the patents and applications by variations in the silver halide, the binder (if present), the organic compounds for insolubilization of silver halide (whose utility can be established by the simple tests defined therein for determination of other useful compounds), the adjuvants generally employed ll'lSllVClf halide systerns the supports, and in the relative concentrations of the various components. Various auxiliary layers may be present, such as abrasion overcoatings, subbing layers, and antihalation undercoats o'r backing layers. The elements may include multilayer as well as monolayer structures, The various layers, including the support, may include inert ingredients, e.g., pigments, organic polymer lattices, and matting agents. As disclosed in US. 3,155,507, the silver halide may be insolubilized by treatment with an appropriateorganic compound either during emulsion manufacture or by treatment'of the coated element with a solution of the organic compound.

The dissolution developer may contain various adjuvants such as shown below in Example III. The only es- K QO g 50.0 KBr g 4.5 H to liter 1 pH 10.45

1 At 0.02 optical transmission density above base plus fog level.

sential components for this invention, however, are water, a silver halide solvent, and a D maintainer. Numerous useful silver halide solvents are disclosed in US. 3,155,507 but in the present application only the use of preferred silver halide solvents which contain the thiosulfate anion will be described.

The invention will be further illustrated by but is not intended to be limited to the following examples.

EXAMPLE I A light-sensitive gelatino-silver chloride coagulum, made by precipitation, coagulation and washing in the manner taught in Moede, US. Patent 2,772,166, was redispersed in an aqueous gelatin solution so as to achieve a gelatin to silver chloride weight ratio of 0.79. The resulting emulsion was digested at 170 F. for 20 minutes in the presence of 0.80 g. of 2-mercapto-4-phenylthiazole and 0.025 g. of the merocyanine of Example I of Kendall U.S.P. 2,342,546, Feb. 22, 1944, per mole of silver chloride. Normal emulsion adjuvants were added, including gelatin hardening agents and coating aids, and the emulsion was coated on a vinylidene chloride copolymer subbed polyster 'base prepared as described in Example IV of Alles, U.S. Patent 2,779,684 (and to which a gelatin sub layer had been subsequently applied), The coating weight was 46 mg./dm. calculated as metallic silver.

Film strips from the gelatino-silver chloride photosoluble film just described were exposed for 10 see.

through a x/fstep wedge spaced 2 ft. from a high intensity, tungsten filament, incandescent lamp (General Electric Reflector Photoflood Lamp, No. PH/RFL 2). Strip No. 1, the control, was processed for 45 sec. in equal parts of water and of the following silver halide solvent solution.

Water ml 800 Na- S O (anhyd.) g 153 Na SO (anhyd) g N32B407' g Glacial acetic acid ml 12 KA1(SO -12 H O -g Water to liter I pH 4.5

Following this dissolution development, the strip was rinsed in water for 15 sec., white fluorescent-room lamps were turned on, the image was intensified for 1 min. in the following solution:

p-Methylaminophenol sulfate 3.0 Hydroquinone g- 9.0 N21 80:, g 50.0

With regard to Table 1, it should be mentioned that Without the D maintainer, considerable density loss would have occurred with the conditions favorable for greater speed and contrast, i.e., high pH and longer processing times.

EXAMPLE II Exposed film strips as described in Example I were processed for 4 minutes at 68 F. in various dissolution developer solutions, then washed, light fogged, intensified in a silver halide photographic developing solution, washed and dried as described in Example I. The control strip (No. 1) was processed in a dissolution developer consisting of 270 nil. of the undiluted silver halide solvent solution of Example I, 4 g. Na SO 2.4 ml. of glacial acetic acid, and adding water to bring the total volume to 300 ml., the pH being 4.8. Strip No. 2 was processed in a similar solution but one which also contained 3 ml. of the D Maintainer 1, 2-dichloroethane, the pH being 4.8 (an optimum pH).

Strip No. 1 had a D of 2.95 and a gamma of 4.05. Strip No. 2, processed in the presence of the D maintainer, had a D of well over 4.0 (the maximum which could be determined with the densitometer in use), had an extremely high gamma of about 28, and had an apparent speed about 5.6 times that of the control (at 0.02 optical transmission density above base plus fog level).

Similar results were obtained using equivalent amounts of 2-butoxyethanol, benzyl acetate, benzyl chloroacetate, triethyl phosphate, benzyl alcohol and bis(Z-chloroethyl) ether as D maintainers.

EXAMPLE III A silver halide solvent solution was prepared like the control solution of Example I except that the pH was 6.0. A number of similar silver halide solvent solutions were prepared but to which was added one of the D maintainer compounds listed below at a concentration of either 0.05 or 0.1 percent by weight.

Exposed film strips as described in Example I were processed for 2 minutes at 68 F. in each of these silver halide solvent solutions. Processing of the films was. then continued as in Example I except that 6 g. of sodium hexametaphosphate were added per liter of the intensifying solution. Results are given in Table 2 and the effectiveness of the D maintainer is indicated by the increase in D (optical transmission density) over the control.

TABLE 2 Organic compounds D maintainer: D None (control) 1.36 CH (CH OH 1.50

gram of 2-niercapto-4-cyclohexylthiazole per mole of (CH COH 2.25 silver halide, on the film base of Example I. The dried 3 2 4 element was then exposed behind a /2 step wedge for a( 2)5 5 seconds to the light source of Example I at a distance a( 2)5 2 5 of about inches. Exposed elements were then immersed 2)s in a dissolution developer (compositions shown in Table H N(CH NH 3) for 30 seconds and 3 minutes, rinsed in water, rc- CH (CH O(CH OH exposed, and bathed in a conventional photographic de- CH (CH OI-I 3.5 veloper of the type given in Example III.

TABLE 3 DH 01 g./liter Dissolution g./1iter gJIiter Din. Dissolution developer developer N32890:; Na SO D Maintainer Maintainer A (control) 5 77 7.5 None 0 B 5 77 7.5 2-butoxyethan0l..- 20

CH (CH COOH .8 20 The maximum transmission optical densities were then (3I-I CH OCH CH 3.0 determined and are listed below. 323 2225 3 Dissolution developer: D after 3 minutes n-Octadecanol 3 (control) u CI-IBr 25 u ClCH CH Cl 2.0 EXAMPLE V z z A photosoluble element was prepared by coating an BfcHzcHzcl aqueous gelatin dispersion of a spectrally sensitized silver BrClrIaCH Q z z 2' chloride which contained the dye of Example I and 1.18 g'gigggzgig gefigg of benzoxazolethiol per mole of silver chloride on the.

e in base of Example I. P- acld The dried element was then exposed and processed as in Example III and using the dissolution develo er as deiP- P scribed in Example IV. Benzoic acid 2.0 g i g g g 5-8 Dmtmafter 30 seconds in... after 3 minutes poro enzoic aci 2,4-dichlorobenzoic acid i iiii ii iigii i?i fil 1.0 0,29 Phthalic acid 2.3 B 1.9 1.05 p-Methylbenzenesulfonic acid 2.1 40 Benzenesulfonic acid 2.2 EXAMPLE VI 4'ami 11-l-naphthalenesulfonfc l Example V was repeated except that 2.4 grams of 1- 2-HI111110-l-naphthalqnesulfomc 361d (1-naphthyl)-2-thiourea per mole of silver chloride was iz p t l t fi fi z s ff & substituted for the benzoxazolethiol.

-nap aquinoneu onic aci Saponin Dim. after 30 seconds om, after 3 minutes 22.22% tiifiii ite 53 iit t if 0 t con ro 0.05 Phenyl acetic acid 3.1 B 0.85 0.33 l-naphthoic acid 3.0 Methyl benzoate EXAMPLE VII Benzyl alcohol Example V was repeated except that 1.5 grams of Hexane p-bromothiophenol per mole of silver chloride was subgyl cloheiranol :2 stituted for the benzoxazolethiol. 6323225113::::::::::::::::::::::1:: 2:1 55 Dissolution developen D... f er 30 Tartaric acid 2.3 (control) Lactic acid 2. 05 Benzyl ether of 2-methoxyethanol 3.4 EXAMPLE VIII .2 gggg i i gg g A photographioelement was prepared by coating an Styrene aqueous gelatin dispersion of silver bromochloride (3O Trianyl g 2 2 m epercent silver bromide and mole percent silver henoxyethanoi chloride) on a film base prepared as in Example IV of zfhen lethanol 5 Alles U.S.P. 2,779,684. After drying, the film Was soaked All; 1 l; h 1 155 5 for 30 sec. in a solution of 0.15 g. of 2,5-dimercaptol 1,3,4-thiadiazole in 500 ml. ethanol-water solution (17 y a C0 0 5-2 parts ethanol-3 parts water) to produce a photosoluble Benzyl ethyl ether eleinent. Exposure and processing were as stated i E Benlene ample IV with exposure times as indicated.

EXAMPLE iv 70 Exposure (seconds) Dmux. after 40 seconds Dissolution developer:

1%. (control) The D maintainers referred to in the first paragraph of the Summary of the Invention (page 1 above) in addition to meeting the requirements in subparagraphs (1), (2) and (3) of said paragraph fall under the general formula:

The compounds listed in Example III fall within three general classifications, namely,

(1) Aliphatic alcohols, ethers and acids,

(2) Aromatic hydrocarbons and nitro, amino, aldehyde, halogen, carboxy and sulfonic acid-substituted aromatic hydrocarbons; and

(3) Halogen and amino-substituted aliphatic hydrocarbon compounds.

Compounds coming within these three classifiications are as follows:

(a) exposing, imagewise, a photosoluble layer containing silver halide made relatively less soluble in a silver halide solvent by treatment with an organic compound capable of forming a silver salt of lower solubility in water than silver chloride and (b) dissolving the exposed silver halide in a silver halide solvent comprising an aqueous bath of an alkali metal or ammonium thiosulfate,

said process being characterized by the presence while said layer is in said bath, at a predetermined pH, of D -maintaining amounts of an auxiliary organic compound different from that in (a) devoid of ionizable iodine or oxidizing or reducing groups which are active at the working pH, said compound having (1) at least one polar or ionic group, (2) at least one hydrocarbon group, and (3) a molecular weight between 61 and 300, the organic compound being present in suflicient quantity to retard solution of the unexposed silver halide and within the range of 0.1 to grams per liter of the aqueous bath.

2. A process according to claim 1 wherein said auxiliary organic compound is present in said bath in the specified quantities.

3. A process according to claim 1 wheerin said auxiliary organic compound is 2-butoxyethanol.

4. A process according to claim 1 wherein said auxiliary organic compound is 1,2-dichloroethane.

5. A process according to claim 1 wherein said auxiliary organic compound is benzyl alcohol.

6. A process according to claim 1 wherein the organic compound of step (a) is present in such an amount, in

Classification (1) Classification (2) Classification (3) CHz(CH2)s-OH- o-Nitro benzoic acid... (C 93011 p-Nitrobenzaldehyde. CH3(CH )4OH p-Nitrobenzoic acid CH3(CH2)5OH o-Nltrotoluene HO (OHmOH o-p-Dlnitrotoluene CH3(CHz)3-O-(CH:)QOH. Benzcic acid 3(0 D1011 o-Chlorobenzoic acid- CHsCHnOCHaCHg p-Chlorobenzolc acid u-Decanol 2,4-dichlorobenzoic aci n-Dodecanol. n-Octadecanol. Cyclohexanol Benzenesulfonic acid Br BICH CHgBf-l-ClCHaCHgCl Benzyl ether of 2-methoxyethanol..- 2-amino l-naphthalene-sulionlc aeid Diethylene glycol--. l-naphthalenesultonic acid Ethylene glycol 1,2-naphthaqmnone-4-snlfonic acid ycerol 4-amino-1-naphthalene sulionic acid Allyl alcohoL. Phenylacetic acid t-Amyl alcohol l-naphthoic acid Benzyl alcohol Methyl benzoate 1 Bcnzylethyl ether CH3(CH2)0COOH Citric acid. Tartaric aci Lactic acid Triallyl citrate--. Z-phenylethane Benzyl acetate 1 Benzyl benzoate l The alcohols formed during hydrolysis fall under the generic formula.

The present invention has the advantages of the basic process of photosolubilization, especially that of a very simple, single step process of obtainin a positive image. Advantages over the basic process include increased optical densities in unexposed or lightly exposed areas, both for silver halide images and for intensified images. Also, processing is simpler because the D maintainers make the effects of such variables as concentration of silver halide solvent, solution of pH, processing times and temperatures less critically. The D maintainers often increase contrast and apparent speed although decreases in one or both of these variables sometimes occur. Thus, by proper selection of the D maintainer and its concentration, another method is available for controlling speed and contrast. Still other advantages will be apparent from the above description of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A photosolubilization process for forming a directpositive silver halide image which comprises:

terms of the ratio of its weight to the surface area of the silver halide crystals, that when admixed in such ratio with an aqueous silver bromochloride, 30/70 mole percent, gelatin dispersion containing 0.29 mg. of Ag in onehalf ml., and said silver bromochloride dispersion is treated with 10% by weight aqueous sodium thiosulfate, so that the resulting mixture contains 0.29 mg. of Ag and mg. of sodium thiosulfate, at least three times the amount of silver bromochloride remains undissolved as compared with a similar dispersion successively treated with 5% by weight aqueous sodium hypochlorite and 10% by weight aqueous sodium thiosulfate, so that the resulting mixture contains 0.29 mg. of Ag, 25 mg. of sodium hypochlorite and 100 mg. of sodium thiosulfate, after vigorous agitation of both dispersions for 30 seconds at 25 C., and the auxiliary compound is added to the bath of step (h) before the layer is added to the bath.

7. A process according to claim 1 wherein the organic compounds of step (b) fall under the general formula:

wherein:

z=0,1; q=0,1,2,3,4; 112k; K=O,1,2; 11:0 to 18; m=0

to 3; but m and n may not both be 0;

pg2(nk)+1; h=0 when m=0; h=1 when m 0 and the numbers are cardinal numbers;

X=Cl, Br, N0 CHYOH, C H YY", H, COOH or CHO; or NH when N 4; or OCH only when m:

Y=Cl, Br, OH, H, COOH, CHO, C H X'X", C H X'X" or NH when n 4;

X'=any value of X except NH 10 X"=any value of X plus SO H; Y'=any value of Y; and Y"=any value of Y.

References Cited UNITED STATES PATENTS 3,155,507 10/1964 Blake 96-64 NORMAN G. TORCHIN, Primary Examiner O R. E. FICHTER, Assistant Examiner 

